Illumination system for communicating data

An uplink subsystem for use in an illumination system arranged for optical communication as well as the illumination system, the system comprising a downlink subsystem and the uplink subsystem. The uplink subsystem comprises sensors (e.g. infrared sensor) embedded in each luminaire in the group. The uplink subsystem also comprises a demodulator, and a distribution network for supplying the signals sensed to an adaptor to combine instances of the sensed uplink signal in a manner that takes into account a Time Division Medium Access scheme and a demodulator to demodulated the combined signal. The system further comprising a downlink subsystem that in turn comprises a modulator for generating a modulated waveform, and an optical fiber distribution network to distribute the modulated waveform to each luminaire in a group. Each such luminaire generates a drive current for driving a lighting element of that luminaire to emit light. Each also injects the modulated waveform into its drive current so as to embed the downlink signal in the emitted light.